The "autocomplete" attribute is now hardcoded to off here:

https://github.com/select2/select2/blob/develop/dist/js/select2.js#L1964
https://github.com/select2/select2/blob/develop/dist/js/select2.js#L4064

Unfortunately, the off value is ignored in Chrome (see here: https://bugs.chromium.org/p/chromium/issues/detail?id=468153#c164)

And this is what happens if you have addresses saved in Chrome and you have forms with a name, address, country etc., the Chrome autocomplete UI goes above the Select2 and it's impossible to see the options:

To fix this, we need to set a custom autocomplete value, ex. autocomplete="campaign-countries".
I think Select2 should implement a way to set a custom value, with an option or by reading it from the original select.